The present invention relates to petroleum refining processes and more particularly involves hydrotreating methods for removal of unwanted sulfur and carbon during the refining of crude oil into gasoline and other hydrocarbon products.
The present invention involves the treatment of feedstocks for supplying fluid catalytic cracking (FCC) reactors. Fluid catalytic cracking is a process for converting high molecular weight hydrocarbons into the more valuable, lighter, low-molecular-weight products by contacting the high molecular weight hydrocarbons with a powdered catalyst under appropriate process conditions. The typical cat cracker process is used to convert excess refinery gas oils and heavier refinery streams into gasoline, C3 and C4 olefins, and light cycle oil. The FCC process in intended to bring refinery output into line with the product market demands. The FCC process is usually the heart of a modern petroleum refinery because of its adaptability to changing feedstocks and product demands and because of the high margins that exist between FCC feedstocks and FCC products. As oil refining has evolved over the last fifty years, the FCC process has evolved with it by allowing the cracking of heavier, more contaminated feedstocks, thereby increasing the operating flexibility of the modern refinery while accommodating environmental legislation and further maximizing reliability.
The modern FCC unit accepts a large and broad range of feedstocks which contributes
Traditional wisdom in the refining industry has indicated that the use of tungsten as a hydrotreater catalyst would be unsuccessful due to the fact that tungsten is too sensitive to sulfur, although tungsten is more active in hydrogenation than conventional materials such as nickel, moly, and cobalt/moly. However, the present inventors have discovered that a nickel-tungsten catalyst (NiW) can be used with a high-sulfur feedstock to increase the production of feedstock material for conventional FCC reactors. By utilizing tungsten instead of molybdenum or cobalt, the refiner can increase the conversion rate in the hydrotreater significantly with only a minimal increase in material cost for the new catalyst. Although the tungsten-on-alumina catalyst has been utilized in hyrdocracking, it has never been believed possible to utilize a nickel-tungsten catalyst for hydrotreating. The present inventors have discovered the process for increased conversion whereby nickel-tungsten may be used for hydrotreating feedstocks for FCC reactors to remove excess carbon and sulfur.